Security services are not contemplated in an appropriate way in the current standards for broadband wireless LANs, namely IEEE 802.11 and HIPERLAN/2. A wrong design of the security architecture, a bad election of cryptographic algorithms and a lack of scalability, are among the criticism that these standards have received. In this paper, the security architecture adopted within the Spanish ICT (Information and Communication Technologies) project DARWIN (Demonstrator of an Adaptive and Reconfigurable Wireless IP Network) is presented. The DARWIN approach, adopting HIPERLAN/2 as a model, incorporates all the basic security services, with a high degree of flexibility and scalability, and correcting some faults of HIPERLAN/2.